No indication of toxicity was detected in rats treated with folate-targeted immunotherapy for 15 weeks. Toxicity analysis associated with continuous treatment of healthy keyhole limpet hemocyanine-fluorescein isothiocyanate (KLH-FITC)-immunized rats with folate-targeted immunotherapy (FTI) for 15 weeks. Non-immunized or KLH-FITC-immunized rats were treated with folate-FITC (300 nmole/kg, three times per week) and sacrificed at the indicated times. Serum was analyzed for indicators of kidney (creatinine) (a) and liver (aspartate aminotransferase [AST-SGOT])(b) function. Tissue samples, including liver, kidney, brain, lungs, and bone marrow, were simultaneously submitted for histopathological analyses. No indication of toxicity was detected by either type of analysis (tissue section data not shown) (mean ± standard deviation, n = 8 rats/group).